--- Howard Winter <HDRW@H2Org.demon.co.uk> wrote:

> Debbie,
> There are a number of ways from adjusting the speed (field coils control
> that), using rotary converters (a motor driving a generator), to converti=
ng =

> to DC and back.  If you have great speed variation then the DC route is
> probably the easiest.
>
> Howard Winter
> St.Albans, England

Thanks guys!

So .... OK when the wind drops and the blades are turning slow, o/p volts a=
re
less than the grid, then it would draw power from the grid. When the wind p=
icks
up, the turbine would then have to "pay back" power into the grid so as to
break even?

I'm just having trouble visualising how the two systems mesh together. As I=
 see
it, the grid's frequency (50Hz) is rock steady 'cause the rotors in the
generators at the (coal-fired) power station weigh many tons and their
rotational inertia doesn't allow the line frequency to vary much at all.
Likewise the 3 phases are locked in  because their voltage is induced by the
moving rotor. Hope I'm on the right track?

The wind turbines, on the other hand, are situated in a cluster on the coas=
t.
The turbulence created by the front row must affect the windflow for the on=
es
behind, I guess? There'd be minor differences in angular speeds for each
machine due to differences in mass, frictional resistance and so on. Also t=
he
position of the blades, hence the position of each turbine rotor wrt the fi=
eld
coils, would be random. So the phases & frequencies would not only vary hug=
ely
from the grid but they'd also be different from turbine to turbine? Yet the
output of the entire turbine farm would have to be synched with the grid v/v
phase and frequency at a total power output of 12MW. Just curious how they =
do
it 'cause it sounds like a "non trivial" problem to me.

If they went for DC -> AC switching, they'd suffer pretty high conversion
losses wouldn't they? Assuming it could be done at Mega-watt levels.
Debbie


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